How to keep relaxed water at start of simulation
Set Flow object to XY dimension of Domain at a bottom so there are not a gaps between Domain boundary and Flow. Like the liquid (Flow) is in a rest shape.

Note: Previously I thought, liquid explosion can be caused by objects intersecting, but it doesn't matter, even with Effector inside - no movement on a surface before Effector starts to &quot;raise&quot;, as you can see in frames 0-30.